(1) Field of the Invention
The present invention relates to the treatment of parts of a plant after they have been removed from the plant to improve the quality of the parts, particularly to reduce or increase the acidity and sugar content in the part. In particular, the present invention relates to the use of L(+) adenosine and 1-triacontanol to treat the plant part to improve the quality of the part.
(2) Prior Art
U.S. Pat. No. 4,849,012 to Wilson describes the use of 1-triacontanol (TRIA) applied to the trees with the fruits to increase the sugar content in oranges. Tests with oranges (Citrus sinensis L.) showed that this increase in sugar was translated into higher brix/acid ratios in the fruit when entire trees were sprayed in the grove as described in U.S. Pat. No. 4,849,012 and Wilson, W. C., et al., Methods for reducing acidity in citrus fruit, Proc. Fla. State Hortic. Soc. 101:157-161 (1988). These increases are economically important to the citrus industry because the value and maturity of citrus fruit is partially determined by its brix/acid ratio. Brix, or % soluble solids, is used as a measurement of the sugar content since sugar is the main component.
The use of TRIA and TRIM to stimulate plant growth is described in U.S. Pat. Nos. 4,150,970 to Ries et al and 4,741,754 to Ries. U.S. Pat. No. 4,333,758 to Welebir also shows TRIA compositions used for this purpose. Foliar applications of micromolar concentrations of TRIA stimulated an increase in reducing sugars and total reducible nitrogen in both whole plants and cell free systems (Houtz, R. L., Development and characterization of an in vitro system responsive to 1-triacontanol. M. S. Thesis, Michigan State University, East Lansing, Mich. (1980)).
U.S. Pat. No. 5,009,698 to Ries, Wert and Nair, describes the use of L(+)adenosine, isolated from TRIM initially and then derived from chemical sources, to stimulate the growth of a plant. The L(+)adenosine is applied early in the growth of the plant and produces significant yield improvements.
Triacontanol (TRIA) is used on millions of hectares to increase crop yield, particularly in Asia. In controlled environment studies, synthetic L(+) adenosine was found to increase the rate of growth of rice seedlings as measured by total dry weight gain, more than 50% within 24 hours of a foliar application of 0.01 to 100.0 .mu.g..L.sup.-1 (3.7.times.10.sup.-11 to 10.sup.-7 M) (Ries, S. K., et al., Plant Growth Reg. 9, 263 (1990)). L(+) adenosine is more consistent than TRIA.
The improvement of fruit quality through the use of chemicals has also received attention, particularly as it pertains to citrus fruits (Monselise, S. P., Scientia Hortic. 11:151-162 (1979)). Arsenic containing compounds, particularly lead arsenate, are widely used in grapefruit (Citrus paradisi Macfadyen) to lower acid and increase the brix/acid ratio (Deszyck, E. J., et al., J. Amer. Soc. Hort. Sci. 75:266-270 (1959)). Many other chemicals are now being tested for this purpose (Tenzer, A. I., Proc Plant Growth Reg. Soc. Amer. 14:316-325 (1987); and 22, 23 and U.S. Pat. No. 4,849,012.
Arsanilic acid has been tested as a substitute for lead arsenate because of concerns about the safety of using inorganic arsenical compounds on food crops. In tests on grapefruit, arsanilic acid was found to increase the brix/acid ratio by decreasing the total acidity, in doses ranging 500 to 6000 mg/liter with 1000-1500 mg/liter being the most effective.
While arsenical compounds have improved the quality of grapefruit, they are not legal for use on oranges because they cause an extreme reduction in acidity [23]. For this reason, other plant growth regulators are now being investigated. In recent trials using foliar sprays before harvest on `Hamlin` and `Valencia` oranges, TRIA reduced the total acidity by an average of 17.5%, increased the brix an average of 16.3%, and increased the brix/acid ratio an average of 41.5% using concentrations of 0.67 and 1.33 ppb. (Wilson, W. C., et al., Methods for reducing acidity in citrus fruit, Proc. Fla. State Hortic. Soc. 101:157-161 (1988)). Other Commercial plant growth regulators such as Citrus 10 and NF-10 are also being tested (Tenzer A. I., Proc. Plant Growth Reg. Soc. 14:316-325 (1987); and (Wilson, W. C., et al., Methods for reducing acidity in citrus fruit, Proc. Fla. State Hortic. Soc. 101:157-161 (1988)). The active compounds in these formulations are not known.